I mean it is a pretty brief time period to be nostalgic over. In USA, any cellphone ownership passed 80% in 2010. That is an overall number. Depending on who and where you are it might have been before or after. I think 80% is "widespread". Smartphones passed 80% in 2019. So you are talking about 9 years.
Source: pew Mobile phone ownership over time
Tbh i do not know if relevant to making/breaking plans because my experience was that as soon as both parties have any kind of mobile device, plans started being more fragile. Not sure if smart/dumb has any impact. Maybe i misunderstood your point...